Toss rhubarb with sugar, cloves and orange zest and juice, then put in a wide skillet. Cook over medium heat, stirring now and then. As soon s rhubarb is tender – some pieces will have fallen apart while others are still whole – transfer it to a bowl and stir in the strawberries and mango. Toss gently, then cover and chill. As it cools, it’s red juices will be released.